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Exam #2 Study Guide 2/29/16 9:20 PM
• Organ system consisting of the brain, spinal cord, and associated nerves that coordinates the other organ systems of the body
• Central nervous system:
• Brain and spinal cord
• Peripheral nervous system:
• Nerves: composed of axons and dendrites
• Divides into:
o Somatic nervous system: nerves that serve the skin, skeletal muscle and tendons, voluntary and involuntary control (reflexes)
o Autonomic nervous system: regulates the activity of cardiac of smooth muscles (many associated with gastrointestinal tract and blood vessels that control blood flow to the body), organs and glands, also
involuntary control (remember: autonomic=automatic things--no control over heart beating etc). Divides into:
???? Sympathetic: activities associated with emergency (fight or
flight) AKA: E division (think of Emergency)
If you want to learn more check out goal displacement, satisficing, and groupthink are
???? Parasympathetic: active under normal conditions (rest and
digestion) AKA: D division (think of Diaresis--production of urine)
1. Receives sensory input: senses (touch, hearing, smell, etc) eg: the smell of baking cookies is picked up by the PNS and that info is sent to the CNS 2. CNS performs information processing and integration: the CNS reviews info and stores it as memories. eg: the smell of baking cookies evokes pleasant memories of their taste
3. CNS generates an appropriate motor response: eg the smell of baking cookies makes the CNS actives the PNS to activate muscles, glands, organs (move to eat the cookies)
• Nervous tissue contains 2 types of cells:
o Neurons: nerve cells that transmit impulses between parts of the nervous system:
o Nerve signal: action potentials traveling along a neuron, conveys info o Action potential: change in electrical conditions at a neurons
membrane (like a line of dominoes, one falls and then each one keeps
falling after that). Normal state: negative on the inside, positive on the
outside: Neuron communication happens through nerve signals and action potential. The inside of the axon is negative and the outside is positive when it's at rest, but when a nerve signal is happening it flips the charges of the inside and the outside.
o Refractory period: portion of axon immediately following the action potential is unable to conduct and action potential that ensures a one way direction of a signal (cell body to axon)
???? Cell body,
???? Sensory neurons: sensory receptors in the PNS that take the info to the CNS
???? Interneurons: found entirely in the CNS (work as a relay) ???? Motor neurons: move the info from the CNS to the PNS so that the body moves
???? (photo showing all types of neurons together) o Neuroglia: nonconducting nerve cells that support the neurons ???? Schwann cells: found connected to the axons, nucleus can be seen, like insulation for the cells, conducts saltatory conduction If you want to learn more check out sicial darwinism
(jumping: the info jumps between cells which is faster--100
• Afferent: going to the spinal cord (the info of the mallot hitting the knee is going to be processed)
• Efferent: away from spinal cord (the info goes to the muscle to make it move) • Na+: sodium, starts an action potential when is rushes inside the plasma membrane causes the flip of the signs
• Membrane potential: difference in electrical change between 2 sides of a membrane. • Resting membrane potential: polarized plasma membrane (-70 mV--you are -70 negative inside compared to the outside), the net number of positively charged ions outside and the negatively charged ions inside it
• Sodium-potassium pump: membrane protein that uses ATP to pump 3 Na+ out and 2 K+ into the cell, there's always going to be a negative charge on the inside of the membrane this way. This sets things up for diffusion, because the Na+ will be in high concentration outside and will want to go inside and vice versa with the K+, when this happens, the action potential is happening. Don't forget about the age old question of michigan state marine biology
• Orange= sodium channel, pink=potassium channel • Potassium can sometimes leak out, this makes the inside even more negative.
• What happens during action potential?
1. Conductance of a nerve signal in axons
2. All or nothing event (either works or doesn't work), self propagating 3. 1st sodium gates open resulting in depolarization (the first domino has fallen down) (once the gate opens, the sodium rushes inside the membrane because of diffusion, so the inside of the membrane will no longer be negative)
4. Next potassium gates open resulting in repolarization (lifting the domino back up) (the potassium rushes outside because of diffusion) Don't forget about the age old question of segmentation contractions
5. Sodium-potassium pump restores original ionic distribution
• Stimulus: activates neuron and begins action potential (causes first domino to fall) if threshold is met (-40 Mv, when the voltage changes from -70 to -40, then the sodium gate opens up), eg: pricked by a pin
• Protein channels (gates):
1. Voltage gated: opens and closes in response to voltage changes across membrane
2. Ligand gated: opens and closes when a specific chemical binds to it 3. Mechanically regulated: responds to physical distortions of the membrane surface
o The junction between neurons (empty space between axon
terminal/presynaptic membrane and cell body or dendrites/postsynaptic membrane); nerve signal can not jump synaptic cleft
1st: presynaptic membrane (axon terminal)
2nd: synaptic cleft
3rd: postsynaptic membrane (usually dendrite)
• Neurotransmitters: chemicals responsible for transmission across a synapse. Closer ti -40mV you will communicate, if its getting further from the -40mV, then no. The
neurotransmitters get out through exocytosis. Stored in synaptic vesicles at axon terminal. Also transmits signal between:
???? Nerve--- muscle
???? Nerve--- organ
???? Nerve--- gland
• Events at synapse:
1. Nerve signal travels along axon to an axon terminal
2. Ca2+ ion gates open and Ca2+ rushes in axon terminal
3. Ca2+ ions promote fusion of synaptic vesicles with presynaptic membrane 4. Exocytosis of neurotransmitter into synaptic cleft and diffusion occurs 5. Neurotransmitters attach to receptors on the postsynaptic membrane. Only single type of channel opens
6. Excitatory or Inhibitory synapse, depending on the neurotransmitter 7. Integration: summing up of excitatory and inhibitory signals
8. Termination of neurotransmitter effects: degraded by enzymes 9. Reuptake by presynaptic membrane
10.Diffusion out of synapse
• Neurotoxins: include numerous chemicals that poison the nerve. Ex. Novocain •
• Central Nervous System: where sensory information is received & motor control is initiated
• Meninges: protective membranes that cover brain and spinal cord. Eg. Meningitis infection of the meninges
• Cerebrospinal fluid: cushions and protects CNS; fills spaces between meninges. Helps maintain blood-brain barrier
• Ventricles: interconnecting chambers that produce and serve as a reservoir for cerebrospinal fluid.
1. Lateral ventricles: proximate to cerebrum
2. Third ventricle: proximate to diencephalon
3. Fourth ventricle: proximate to cerebellum (extends all the way down to the spinal cord)
• Grey matter: contains cell bodies and short, nonmyelinated fibers • White matter: contains neuron fibers that run together in bundles called tracts (the myelinated axons make it look white):
o Ascending tracts take info to the brain
o Descending tracts take info away from the brain
o Tracts cross paths just after they enter and exit the brain
• (spinal cord diagram)
• Spinal cord: extends from base of brain and proceeds inferiorly in the vertebral column, allow for communication between brain and peripheral nerves, center for thousands of reflex arcs. Has grey matter on the inside and it looks like a butterfly, white matter on the outside (opposite to brain--brain has white inside and grey outside).
o The bulb structure (dorsal root) is where the sensory information goes to brain and is ascending
o The ventral root is of motor neurons that is descending
• Brain: enlarged superior portion of the CNS located in cranial cavity of the skull o Cerebrum: largest part of brain, consists of 2 cerebral hemispheres (left and right). communicates with and coordinates the activities of the other parts of the brain
???? Left hemisphere: has greater control over language and mathematical abilities, logic, analysis
???? Right hemisphere: more visual-spatial skills, intuition, emotion and art and music
o Sulci: grooves that divide each hemisphere into lobes:
i. Frontal lobe: motor functions, permits voluntary muscle control, enables one to think, problem solve, speak and smell
i. Parietal lobe: receives info from sensory receptors in skin and taste receptors in mouth
ii. Occipital lobe: interprets visual input and combines it with other sensory experiences
iii. Temporal lobe: sensory areas for hearing and smell
o Cerebral cortex: outer layer of cerebral hemisphere, composed of grey matter, receives sensory info and controls motor activity. Accounts for sensation, voluntary movement and thought processes. Very thin layer (2-4mm) but makes up 40% of the biomass of the brain and has over 1 billion cell bodies. Enables us to perceive, communicate, remember, understand, appreciate and initiate voluntary movements (associated with consciousness).
???? Higher mental functions: memory (ability to hold a thought in mind or recall events from the past) and learning (retain information)
o Diencephalon: part of the forebrain between the 2 hemispheres and midbrain. has the thalamus, 3rd ventricle and hypothalamus
o Thalamus: "gatekeeper to the cerebrum" by controlling which received sensory info are passed on to the cerebrum (filters noises you don't pick up for example)
o Hypothalamus: helps maintain homeostasis: regulates hunger, sleep, thirst, body temp, heart rate, etc and forms floor of 3rd ventricle.
o Corpus callosum: extensive bridge of nerve tracts, enables communication between left and right hemispheres
o Cerebellum: coordinates equilibrium and motor activity to produce smooth movement (looks like a tree)
o Hypothalamus: endocrine system (hormone secretion)
o Brain stem: contains midbrain pons and medulla oblongata
o Midbrain: bellow thalamus and above pons. Reflex centers for the eye muscles and tracts (closing eye/flinching/blinking)
o Pons: bellow midbrain and above medulla oblongata. Assist the medulla oblongata in regulating breathing rate. Respiratory reflexes: apneumatic (stop breathing while sleeping/doesn't allow you to hold your breath very long--cant die) and pneumotaxic (allows for normal shallow breathing). Provides linkage between upper and lower levels of the CNS.
o Medulla oblongata: posteriorest part of the brain stem. Where tracts (from Right to left) cross. Regulates heartbeat blood pressure and breathing. Reflex centers: sneezing coughing hiccupping and swallowing
• General sense: touch
• General sensory receptors:
1. Mechanoreceptors: touch pressure vibration and strech
2. Thermoreceptors: temp changes (located in hypothalamus and skin) 3. Nociceptors: pain: respond to damaging stimuli
• Skin: composed of epidermis (outermost layer), dermis (thick, has cutaneous receptors)
o Knee jerk reflex (patellar reflex) involves mechanoreceptors to maintain muscle tone and posture, detects degree of muscle relaxation and stretch of tendons. Usually involves only 2 neurons (a sensory and a motor-- its faster)
???? Muscle spindle: sensory nerve endings wrapped around thin muscle cells
???? Muscle relaxes and increases length thus stretching muscle spindle ???? Nerve signal is generated, the more the muscle is stretched the faster the neuron fires
???? Reflex action results in contraction of muscle fibers adjoining the muscle spindle
• Special senses: hearing vision taste smell and balance
• Sensory receptor: dendritic end organs or parts of other cell types specialized to respond to a stimulus
• Sensation: conscious perception of a stimuli
• Sensory adaptation: when we stop taking into account a sense after its been consistent after a long period of time (why we cant smell our perfume after a while even though its there)
• Chemoreceptors: respond to chemical substances (are plasma membrane receptors that bind to specific molecules) (olfatory and taste cells)
• Taste buds: sense organ containing receptors for taste. Approx 10000 in adults most in tongue. Includes supporting cells and taste cells that end with microvilli. When molecules bind to receptor proteins of microvilli, nerve signals are generated. 4 primary types of taste (saliva is needed to taste)
• Olfactory cells: located within olfactory epithelia high in the roof of the nasal cavity.10 to 20 million in adult humans. Modified neurons, each with tuft of 6 to 12 olfactory cilia. Each olfactory cell has only 1 type of several hundred possible receptor proteins
• Types of Sensory Receptors Associated with Sight:
1. Photoreceptors: sensory receptor in the retina that responds to light stimuli.
o Rod cells: dim-light and peripheral vision receptors; more numerous. Ubiquitous throughout the entire retina except the fovea centralis (no color vision). When rod absorbs light, rhodopsin splits into opsin and retinal. A cascade of reactions results in ion channels closing in rod
o Cone cells: operate in bright light and provide high-acuity color vision. Located primarily in the fovea centralis. Slight differences in protein opsin structure account for three different types of cones: B (blue), G (green), R (red)
• Parts of the eye:
• Retina: innermost layer of the eyeball that contains rod and cone cells • Fovea centralis: small pit where cones are densely packed (light is normally focused on the fovea)
• Optic nerve: sensory fibers from the retina that take nerve signals to the visual cortex
• Lens: capable of changing shape too focus on things in a far distance or in a small distance. When one gets older older, it starts getting more difficult for it to change shape.
• Rhodopsin: complex molecule made up of the protein opsin and the light absorbing molecule retinal
• Types of Sensory Receptors Associated with Hearing:
• Mechanoreceptors: stimulated by mechanical forces when they or adjacent tissue are deformed by touch, pressure, vibrations, and stretch. Cells that are going to respond to mechanical stimuli
• Hair cells: cell with stereocilia (long microvilli) that is sensitive to mechanical stimulation
• Mechanoreceptors for hearing and equilibrium are located in the inner ear • The Ear:
• Outer ear: functions in hearing; filled with air. The sound waves pass through here
o Pinna: the external ear flap that catches sound waves
o Auditory canal: directs sound waves to the tympanic membrane. Not the same as the auditory tube → auditory tube is much smaller than the auditory canal.
o Fine hairs and modified sweat glands that secrete earwax (cerumen) • Middle ear: functions in hearing; filled with air.
o Tympanic membrane (eardrum): vibrates to carry the wave to three small bones (ossicles)
o Ossicles: amplify sound waves x20 → smallest bones in the body. ???? Malleus
???? Stapes: called this because it looks like the stirrup (the thing that you put your feet on to ride a horse). It kicks on the oval window
each time it vibrates (after oval window there's the liquid of the
o Eustachian tube (auditory tube): equalizes pressure so the eardrum doesn't burst. Connects throat to the middle ear
• Inner ear: functions in hearing and balance; filled with fluid. Important for both hearing and balance
o Cochlea: converts vibrations into nerve impulses
???? Organ of Corti: spiral organ (looks like a snail), contains hairs
that bend with vibrations or waves, this sends impulses to the
cochlear nerve that sends them to the brain. Pitch is determined
by varying wave frequencies detected by different parts of this
organ. Volume is determined by the amplitude of the wave.
o Semicircular canals: rational equilibrium, 3 canals
???? Detects angular movement (rotational equilibrium)
???? Depends on hair cells at the base of each canal (ampulla), they are embedded in cupula
o Vestibule: gravitational equilibrium,
???? Utricule: hair cells that have a jelly-like membrane on top, it
swings the opposite direction of the movement. You know which
way you're going (horizontally) even if you have your eyes
closed. In a horizontal plane
???? Saccule: in a vertical plane, helps to know if you're going up or
down, the jelly-like membrane on top of hair cells swings the
opposite direction of the movement.
• Auditory tube: equalizes pressure in the ear, connects the middle ear to the back of the throat
• How we hear:
1. Pinna catches sound waves
2. Auditory canal directs sound waves to tympanic membrane
3. Tympanic membrane vibrates and wave is carried to ossicles (little bones) 4. Stapes vibrates and strikes the membrane of the oval window
5. Vibration of oval window causes fluid waves within the cochlea
6. Pressure waves move from vestibular canal to tympanic canal crossing basilar membrane
7. Basilar membrane moves up and down, stereocilia of hair cells embedded intectorial membrane bend
8. Nerve signal begins in the cochlear nerve and travels to the brain • Round window: relieves pressure
• It's a type of connective tissue in which cells are separated by plasma • Plasma: liquid portion (90% is water) of blood ( makes up 55% of blood)that includes nutrients, waste, salts, and proteins. Types of plasma proteins:
1. Albumins: contribute to the plasma's osmotic pressure (water pressure, like little sponges that absorb the water so that it doesn't leak out of veins), found in egg whites
2. Globulins: antibodies, hemoglobin (provide oxygen), etc (like an archer's arrows that are made of globulin, that attack any virus or pathogen) 3. Fibrinogen: forms blood clots when activated, blood clots are important so that when we cut ourselves we don't keep on bleeding forever.
• Test question: which proteins are associated with blood?
• Formed element: includes red and white blood cells and platelets, make up 45% of blood
• Platelet: aka thrombocyte, cell fragments of Megakaryocyte, involved in clotting • Functions of blood:
1. Primary transport medium: carries oxygen, CO2, hormones, nutrients, etc 2. Defends against pathogens and helps seal damaged blood vessels: antibodies, phagocytes and platelets do this
3. Regulatory functions: regulates temperature, osmotic pressure, buffers to stabilize the pH 7.4
• Red blood cells: aka RBC, erythrocyte. Contains the protein hemoglobin. Produced in red bone marrow. It looks like a pizza dough because it has a larger surface area this way
• Hemoglobin: has iron and carries oxygen. Each one contains 4 heme groups (little proteins) and each heme group can transport 1 oxygen molecule, so one hemoglobin protein carries 4 oxygen molecules. Approx. 280 million hemoglobin molecules in one red blood cell. Carbon monoxide binds more strongly to the heme than oxygen, this is bad because it leads to us not being able to breathe in situations like being in a garage with car running and door closed.
• Anemia: insufficiency in the oxygen carrying ability of blood, due to shortage of hemoglobin. Females are more likely to be anemic because of the loss of blood they experience every month in their period (approx. 35 ml each period)
• If you go to a higher place like a mountain where there's less oxygen, there's gonna be a low level of oxygen in the blood so the kidney will produce a hormone called erythropoietin that will cause stem cells to increase red blood cell production in red bone marrow so that the blood's oxygen level returns to normal (see picture below) •
• Clotting: process of blood coagulation, usually initiated when injury occurs 1. Blood vessel is punctured
2. Platelets congregate and form a plug
3. Platelets and damaged tissue cells release prothrombin (like scissors, super sharp) activator (this activator will "remove the safety lock on the scissors, and turn prothrombin intro thrombin) which initiates a cascade of enzymatic reactions
4. Fibrin threads form and trap red blood cells
• Blood transfusions: whole blood of just a component of blood (red blood cells, etc), introduced into the bloodstream
• Agglutination: clumping of red blood cells due to reaction of antigens on red blood cell surface and antibody in the plasma. Happens when two blood types that aren't supposed to mix, mix during a transfusion, causes the blood to become more solid instead of a liquid form.
• ABO blood typing: based on the presence or absence of 2 possible antigens (Type A antigen or type B antigen). Depending on the blood type, the rbc produces different antibodies.
• Type A: red blood cells have type A surface antigens. Plasma has anti-B antibodies that look like Y
• Type B: rbc have type B surface antigens, plasma has anti-A antibodies that look like a moon.
• Type AB: rbc have both type A and type B surface antigens, and the plasma does not have type A or type B antibodies.
• Type O: rbc have neither type A or type B surface antigens, plasma has both anti-A and anti-B antigens.
• Test question: what blood types can safely donate blood to a type O? Only a person with type O, because type O has antibodies against type A and type B. •
• When your antibodies attack your own rbc, then you have an autoimmune disease. • Rh blood groups: based on the presence of Rh factor (antigen) on rbc • Rh-: has antibodies against Rh+
• Rh+: 85% of Americans are this type
• Hemolytic disease of newborn (HDN): happens in a newborn when the mother is Rh and the father is Rh+. In a normal pregnancy no blood is mixed between mother and baby, but when the baby is coming out, things can get messy and blood can mix. So if the baby is Rh+, the blood from the mother containing Rh- will have antigens that
attack the baby's rbc.
• RhoGAM is an antibody that is administered around 7 months into the pregnancy, contains small amount of antibodies that attack the baby's rbc if they leak into the mother's blood, quickly so that the mother doesn't produce many antibodies that attack the baby, so both the baby and the mother are safe.
• Organ system in which blood vessels distribute blood by the pumping action of the heart.
1. Heart: muscular organ located in the thoracic cavity. Rhythmic contractions maintain blood circulation
2. Blood vessels: closed delivery system that begins and ends at the heart.
1. Contraction of the heart generates blood pressure (moves blood) 2. Blood vessels transport blood from heart to arteries (big transport vessels, like the turnpike or the i-95), capillaries (where all the action takes place) and veins (to go back to the heart)
3. Gas exchange occurs at the capillaries (CO2 is picked up and O2 is dropped off--because the cells need the O2 for cellular respiration). Nutrients are delivered to the cells by blood, while the blood picks up their waste.
4. Heart and blood vessels regulate blood flow, according to the body's needs • It has to send blood to the kidneys for the blood to be cleansed, to the digestive system to pick up the nutrients from the food we ate, to the respiratory system to pick up the oxygen (because after taking oxygen to the cells, the blood leaves without oxygen and needs more)
• Types of blood vessels:
1. Arteries: they conduct blood away from the heart, they carry oxygenated blood (has one exception)
2. Capillaries: smallest of the blood vessels (it has to be small so that diffusion can take place), takes oxygen to the cells and exchanges it with CO2, "where all the action happens"
3. Veins: they return blood towards the heart. Always have deoxygenated blood (has only 1 exception)
• (the little dots in the purple parts are nucleuses) • Capillaries: found between veins and arteries, very small and diffusion happens very easily and quickly in them
• Smallest blood vessels
• In some cases, only one endothelial cell forms the entire circumference (they are just 1 cell thick)
• They provide for exchange of materials like gases, nutrients, etc by diffusion.
• Arterial system: the arteries near the heart withstand and smooth out large pressure fluctuations, they expand and recoil as the heart beats to propel blood onward • Pulmonary Artery: exception to the rule, it carries deoxygenated blood (takes it to the lungs)
• Pulmonary vein: only vein that is oxygenated in the body
• Arterioles: small arteries,
• When the muscle fibers contract, the vessel constrict; when the muscle fibers relaxes, the vessel dilates.
• Constriction or dilation controls blood pressure
• They lead into the capillary bed
• Capillary bed: interweaving network of capillaries
• Pre-capillary sphincter: controls blood flow through a capillary bed (sends it through something like a shortcut). It's regulated by vasomotor nerve fibers and local chemical conditions.
• Arteriovenuous shunt: enables blood to pass directly from an arteriole to a venule (the shortcut mentioned above)
• Veins: same 3 layers as arteries, but less smooth muscle and connective tissue, they have thinner walls and they have valves
• Venous valves: they resemble semilunar valves in heart in structure and function, so what they do is prevent blood to go backwards. They are most abundant in veins of the limbs. They depend on our movement, if we cross our legs we smush some veins and the blood is forced to go back to the heart.
• Varicose veins: veins that have become dilated because of damaged valves. They can be influenced by: heredity, obesity, prolonged standing, pregnancy (they go away after pregnancy). Eg: hemorrhoids, they are varicose veins in the anus.
• Venules: small veins that drain blood from the capillaries.
• Heart: muscular organ located in the thoracic cavity. Like a double pump. Its rhythmic contractions maintain blood circulation. Left side is systemic (body), right is to the lungs, that blood doesn't mix. Has 4 chambers (left and right atriums and ventricles). Authorhythmicity: it beats on its own and never gets a rest.
• Myocardium: composed of cardiac muscle formed by muscle fibers tightly joined together by intercalated disks (like puzzle pieces):
o Gap junctions: aid in simultaneous contractions of cardiac fibers o Desmosomes: protein fibers that prevent overstretching of the heart
• Pericardium: protective membrane that surrounds the heart and secretes pericardial fluid (a lubrication fluid that allows the heart to move freely without friction)
• Septum: wall that separates the right and left sides of the heart, so that oxygen poor blood and oxygen rich blood never mix
• Atrium: superior chambers (left and right) that receive blood • Ventricles: inferior chambers (left and right)
• Atrioventricular valves (AV): located between the atrium and the ventricles and prevent backflow of blood into the atria when ventricles are contracting: o Tricuspid: right side of the heart
o Bicuspid: aka Mitral valve, left side
• Semilunar valves: prevent blood return into the ventricles after contraction • Heart strings (chordae tendineae): prevent the flaps of the valves from overextending, like a tight seal, prevent valves from inverting.
• Sound of the heart is called "Lub-Dub": Lub is the AV valves slamming shut, the Dub is when the semilunar valves slam shut.
• Heart murmur: a leaky AV valve, a sight swishing sound after the "Lub" • Systemic circuit: blood vessels transport oxygenated blood from left ventricle to body, deoxygenated blood returns to right atrium
• Pulmonary circuit: blood vessels that take deoxygenated blood from right vent to lungs, oxygen blood returns to left atrium
• Coronary artery: supplies blood oxygen and food to the wall of the heart (septum). If a person eats a lot of fatty foods, plaque accumulates and creates a blocked coronary artery results in a myocardial infarction. To solve this, surgeons create a bypass surgery.
• Cardiac cycle: one heart beat, composed of two parts:
o Systole: contraction
o Diastole: relaxation
• When doctors take blood pressure, they look for the first beat and the last beat after the thing around the arm is loosened and the blood starts going to
the arm again. The result will show (for example): 120/80 pressure, 120 is systole and the 80 is diastole.
• Diastole is more stable, it doesn't change if we are anxious or not. • Normal blood pressure reading: below 120/below80
• Cardiac conduction system:
• SA (sinoatrial) node:
o Specialized myocardial cells in the wall of the right atrium
o Like the pacemaker of the heart, 70 beats per minute
o Initiates the heartbeat, sends the information to the heart
o If this node is damaged, you will only have 50 beats per min
• AV (atrioventricular) node: specialized mass of conducting cells located at the atrioventricular junction in the heart. If this node is damaged, you will only have 30 beats per min
• There's a space between the two nodes so that there's time between electrical impulses. So that the atria contract before the ventricles.
• Nodes create the information that makes the parts of the heart contract, like the brain sends signals to the body for it to move via neurons, the nodes are like the brain and send the signals through the atrioventricular bundle and the Purkinje fibers.
• Atrioventricular bundle: bundle of specialized fibers that conduct impulses from the AV node to the right and left ventricles. (they carry the information that the nodes send: it tells them to contract or not)
• Purkinje fibers: modified cardiac muscle fibers of the cardiac conduction system
• ECG (Electrocardiogram): recording of electrical activity associated with the heartbeat.
• P wave: atria about to contract
• QRS wave: ventricles about to contract
• T wave: ventricular muscle fiber recovery
• Ventricular fibrillation: the heart is not pumping properly.
o When this happens, the person needs to be defibrillated using the 2 shock things that are put on people's chest in movies, and the doctors say "clear". What this does is apply a strong electrical current for short time so that all heart cells discharge electricity at once.
• Gastrointestinal tract: a continuous hollow tube extending from the mouth to the anus. AKA: alimentary tract
• It's made up of the:
• Oral cavity: the mouth
• Pharynx: the back of the throat
• Small intestine: absorbs nutrients
• Large intestine: absorbs water
• About 30 feet long in humans
• Accesory organs: the ones that aren't part of the tubing (tract)
• 5 processes necessary so that the digestive process happens: 1. Ingestion: taking of food or liquid into the body through the mouth 2. Digestion: breaking down of large nutrient molecules into smaller molecules that can be absorbed
o Mechanical digestion: cutting and mastication of food, peristalsis o Chemical digestion: digestive enzymes hydrolyze macromolecules 3. Movement (mixing): food is passed from one organ to the next via peristalsis 4. Absorption: taking in of subunit molecules (like sugars, etc) by cells or membranes. Happens in the small intestine
5. Elimination: process of expelling substances from the body via defecation (pooping)
• Peristalsis: we don't have to think about our body digesting to make it happen, it happens on its own.
• Reverse peristalsis: when there's something wrong with the food and makes us vomit or expel it.
• Smooth muscles have peristalsis, except the bladder which is a smooth muscle but we have control over it (if we didn't we would pee our pants all the time)